Silicon Acoustic Wave Substrate Tuning for Stable Higher Modes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic wave devices with silicon support substrates face issues due to variations in acoustic velocity and frequency positions of higher modes, leading to increased likelihood of undesired frequency responses.
Innovation Solution
The acoustic wave device incorporates a silicon support substrate with a piezoelectric body and an interdigital transducer electrode, where the acoustic velocity is set to be higher than 5500 m/s, and a low acoustic velocity material layer is used between the support substrate and the piezoelectric body to stabilize frequency positions and reduce energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silicon support substrate is used for acoustic wave devices, then heat resistance and mechanical strength are improved, but the acoustic velocity varies depending on crystal orientation, causing frequency positions of higher modes to vary and increasing the likelihood of undesired frequency responses
Solution Approach 1:
The patent changes the acoustic velocity parameter of the silicon support substrate by selecting specific crystal orientations (e.g., <100>, <110>, or <111> directions) to achieve a predetermined acoustic velocity range (4000-6000 m/s). This parameter change stabilizes the frequency positions of higher modes and prevents undesired frequency responses while maintaining the mechanical strength benefits of silicon substrates.
2Ease of manufacture
If the acoustic velocity of bulk waves in the silicon support substrate is not controlled, then manufacturing flexibility is maintained, but the frequency positions of higher modes vary, leading to increased energy loss and reduced quality factor
Solution Approach 1:
The patent establishes specific parameter ranges for acoustic velocity (4000-6000 m/s) and crystal orientation (<100>, <110>, or <111> directions) of the silicon support substrate. By controlling these parameters, the frequency positions of higher modes are stabilized, which reduces energy loss and increases the quality factor while still allowing manufacturing flexibility within the specified parameter ranges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively stabilizes the frequency positions of higher modes, reduces energy loss, and increases the quality factor of the acoustic wave device, preventing undesirable frequency responses and improving filter characteristics.
Implementation Method 1
a piezoelectric body provided directly or indirectly on the support substrate, the piezoelectric body including a pair of main surfaces facing each other, and an interdigital transducer electrode provided directly or indirectly on at least one of the main surfaces of the piezoelectric body
Data Source
AI summary
An acoustic wave device includes a support substrate made of silicon, a piezoelectric body provided directly or indirectly on the support substrate, the piezoelectric body including a pair of main surfaces facing each other, and an interdigital transducer electrode provided directly or indirectly on at least one of the main surfaces of the piezoelectric body, a wave length that is determined by an electrode finger pitch of the interdigital transducer electrode being λ. An acoustic velocity VSi=(V1)1/2 of bulk waves that propagate in the support substrate, which is determined by V1 out of solutions V1, V2, V3 of x derived from the expression, Ax3+Bx2+Cx+D=0, is higher than or equal to about 5500 m/s.